David A. Mills was born in Salem on October 9, 1942. He earned a B.S., with honors, from Boston College in 1964 and a J.D. degree from Boston College Law School in 1967, where he was a member and managing editor of the Law Review.
After serving as a law clerk to United States Judge Hugh H. Bownes of the District of New Hampshire, he became an assistant district attorney in Middlesex County. In 1972, Justice Mills joined the Massachusetts Attorney General's office as chief of that agency's criminal appellate section. In 1975, he established a private practice with a concentration in the use, misuse, and reuse of urban land, as well as municipal government.
Governor Jane Swift appointed him to the Appeals Court and he was sworn in on October 18, 2001. Justice Mills is a former chair of the Board of Trustees of the Essex Agricultural and Technical Institute, was a member of the Danvers town meeting for more than thirty years, and is a former town moderator. He presented on criminal law and land use topics for MCLE for more than thirty years continuously. He was awarded the LAMBDA Student Association at Boston College Law School's Integrity Award in 1993. He served as an associate justice until he reached the mandatory retirement age in 2012.